diff --git a/vendor/go.etcd.io/etcd/pkg/transport/limit_listen.go b/vendor/go.etcd.io/etcd/pkg/transport/limit_listen.go
new file mode 100644
index 0000000..930c542
--- /dev/null
+++ b/vendor/go.etcd.io/etcd/pkg/transport/limit_listen.go
@@ -0,0 +1,80 @@
+// Copyright 2013 The etcd Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package transport provides network utility functions, complementing the more
+// common ones in the net package.
+package transport
+
+import (
+	"errors"
+	"net"
+	"sync"
+	"time"
+)
+
+var (
+	ErrNotTCP = errors.New("only tcp connections have keepalive")
+)
+
+// LimitListener returns a Listener that accepts at most n simultaneous
+// connections from the provided Listener.
+func LimitListener(l net.Listener, n int) net.Listener {
+	return &limitListener{l, make(chan struct{}, n)}
+}
+
+type limitListener struct {
+	net.Listener
+	sem chan struct{}
+}
+
+func (l *limitListener) acquire() { l.sem <- struct{}{} }
+func (l *limitListener) release() { <-l.sem }
+
+func (l *limitListener) Accept() (net.Conn, error) {
+	l.acquire()
+	c, err := l.Listener.Accept()
+	if err != nil {
+		l.release()
+		return nil, err
+	}
+	return &limitListenerConn{Conn: c, release: l.release}, nil
+}
+
+type limitListenerConn struct {
+	net.Conn
+	releaseOnce sync.Once
+	release     func()
+}
+
+func (l *limitListenerConn) Close() error {
+	err := l.Conn.Close()
+	l.releaseOnce.Do(l.release)
+	return err
+}
+
+func (l *limitListenerConn) SetKeepAlive(doKeepAlive bool) error {
+	tcpc, ok := l.Conn.(*net.TCPConn)
+	if !ok {
+		return ErrNotTCP
+	}
+	return tcpc.SetKeepAlive(doKeepAlive)
+}
+
+func (l *limitListenerConn) SetKeepAlivePeriod(d time.Duration) error {
+	tcpc, ok := l.Conn.(*net.TCPConn)
+	if !ok {
+		return ErrNotTCP
+	}
+	return tcpc.SetKeepAlivePeriod(d)
+}